The present invention relates generally to translator circuits, and more specifically, to transistor-transistor logic (TTL) to emitter coupled logic (ECL) translator circuits for receiving TTL voltage level input signals and generating ECL voltage level output signals.
TTL circuitry and ECL circuitry are two well-known types of digital circuitry for use in computers and other logic devices. In TTL circuitry a binary "1" is represented by a high voltage level between 2.5 and 5 volts, and a binary "0" is represented by a low voltage level between 0 and 0.8 volts. TTL circuitry is generally known for having high speed and low power requirements.
ECL circuitry generally operates at negative voltage with the high and low level voltage signals established on either side of a negative reference voltage. For example, if a reference voltage is -1.2 volts, a binary "1" may be represented by a voltage level of -0.8 volts and a binary "0" may be represented by a voltage level of -1.2 volts. ECL circuitry is generally known for higher speed switches.
To obtain the advantages of both TTL and ECL circuitry and devices, translators are required for translating the binary data from the TTL voltage level to the ECL voltage level.
One such TTL to ECL translator is illustrated in FIG. 1 as disclosed in U.S. Pat. No. 4,806,800. A TTL input signal is received at input node "A," and a corresponding ECL output signal is generated at node YA. This device includes a TTL input clamped level shifting comparator (transistors Q1, Q2 and Q3 plus resistor R1), a self-centering reference threshold translator (transistors Q7, Q8, Q10 and Q15 plus resistors R5, R6 and R12), a clamped level shifted input translator (transistors Q4, Q5 and Q14 plus resistors R3, R4 and R10), and an ECL Buffer Driver (transistors Q11, Q12 and Q13 plus resistors R7, R8 and R11). However, as with many other TTL to ECL translators, this circuit is large, slow, and inefficient. The number of resistors and switches and the large internal voltage swing slow the circuit. In addition, the large number of devices, especially resistors, increases the required area for the circuit and causes the circuit to dissipate a large amount of power.